30,000 Tons beneath the Sea

__"Burial of Radioactive Waste under the Seabed" by Charles D. Hollister and Steven Nadis, in Scientific American (Jan. 1998), 415 Madison Ave., New York, N.Y. 10017–1111.__

When it comes to the disposal of nuclear waste, many Americans seem to prefer to bury their heads in the sand. A repository has been under development at Yucca Mountain, Nevada, for more than a decade, at least in theory, but no construction has begun and state officials and residents remain adamantly opposed to the facility. It may never open for use. Yet more than 30,000 metric tons of high-level radioactive waste now lie in temporary storage at U.S. nuclear power plants, and every year brings another 2,000 metric tons. Add to that at least 50 metric tons of excess plutonium, and hundreds of tons of highly enriched uranium taken from dismantled nuclear weapons.

Hollister, a vice president of the Woods Hole Oceanographic Institution, in Massachusetts, and Nadis, a science writer, have a different solution to the problem of radioactive waste: bury it beneath the ocean floor.

Marine scientists have identified broad zones of suboceanic terrain in the Atlantic and Pacific that have remained geologically inert for tens of millions of years in the dark and frigid depths. Three or so miles below the surface, note the authors, lie vast mudflats, with a clay-rich blanket, hundreds of meters thick, above the underlying rocky crust. Present evidence, they say, "suggests that mobile, multicellular lifeforms inhabit only the top meter or so of the abyssal clays," and that below that there are no organisms capable of transporting radioactive substances up to the sea floor. Employing technology that has been in use in the petroleum industry for decades, canisters of radioactive waste could be lowered into cylindrical shafts drilled hundreds of meters deep in the thick sediment, well below the ocean floor.

The cannisters themselves would last only a few thousand years at most, but "the muddy clays, which cling tenaciously to plutonium and many other radioactive elements, would prevent these substances from seeping into the waters above," the authors say. Scientists have concluded from experiments that plutonium would not migrate from a breached cannister more than a few meters, even after 100,000 years. Burial of the radioactive waste in the sediments "would most likely buy enough time for the radioactivity of all the waste either to decay or to dissipate to levels below those found naturally in seawater."

Yes, more research is needed, but there has never been a serious challenge to subseabed disposal on technical or scientific grounds, Hollister and Nadis say. Persuading the public is another matter, of course, but subseabed burial, the authors observe, has at least this advantage: it won’t produce "not in my backyard" (NIMBY) opposition.